三种上颌快速扩弓方式扩弓效果的三维有限元分析

Effect of three types of rapid maxillary expansion： a three-dimensional finite element study

目的 通过三维有限元法比较三种上颌快速扩弓方式下牙齿、牙槽骨、腭中缝的横向位移、应力分布和变化趋势,为临床提供参考.方法 对1名来自兰州大学的20岁正常女性志愿者的头部进行锥形束CT扫描取得图像数据,用Mimics和Geomagic Studio软件进行上颌复合体三维重建,用ANSYS Workbench软件建立Hyrax、Haas扩弓器及种植体支抗辅助上颌快速扩弓器（miniscrew-assisted rapid palatal expander,MARPE）3种扩弓器模型,装配并加载强制位移,比较牙齿、牙槽骨、腭中缝的应力分布、变化趋势和横向位移.结果 Hyrax扩弓器牙冠最大横向位移为0.105 mm,腭中缝宽度最大增加0.022 mm,上颌骨呈楔形打开,有顺时针旋转的趋势;Haas扩弓器扩弓效果较好,牙冠最大横向位移为0.216 mm,腭中缝宽度最大增加0.031 mm,应力分布较均匀;MARPE扩弓器牙冠最大横向位移为0.267 mm,腭中缝宽度最大增加0.315 mm,扩弓量及应力最大值出现在中段,有逆时针旋转的趋势.结论 MARPE的骨性改变最显著,Haas扩弓器比Hyrax扩弓器有一定优势.

Objective To evaluate the transverse displacement, stress distribution and tendency of change in tooth, alveolar bone and mid-palatal suture using three kinds of rapid maxillary expansion methods. Methods Cone-beam CT image data was obtained by scanning skulls of a volunteer. Three-dimensional models of maxillary complex were re-established using Mimics and Geomagic Studio and models of Hyrax expander, Haas expander and miniscrew-assisted rapid palatal expander （MARPE） were established using ANSYS Workbench. Stress distribution, displacement and tendency of change in tooth, alveolar bone and mid-palatal suture were evaluated. Results Hyrax expander brought 0.105 mm lateral displacement of crown, 0.022 mm mid-palatal suture width increase, wedge opening and clockwise rotation tendency of maxilla. Haas expander created uniform stress distribution, 0.216 mm lateral displacement of crown, and 0.031 mm mid-palatal suture width increase. In MARPE model, the lateral displacement of crown was 0.267 mm, and mid-palatal suture width increased 0.315 mm. The maximum of mid-palatal suture expansion and stress distribution appeared in the middle region, and maxilla had tendency of counterclockwise rotation. Conclusions The lateral changes of teeth and bones brought by MARPE were the most significant. Haas expander had some advantages in comparison with Hyrax.